1. Field of the Invention
The present invention relates to a semiconductor device and a manufacturing method of the same, and particularly relates to a stacked type semiconductor device in which a semiconductor device is laid on a semiconductor device, and a manufacturing method of the same.
2. Description of the Related Art
As a package structure for achieving improvement in the degree of integration and reduction in size and weight of a semiconductor device, surface-mounting type semiconductor devices which are called BGA (Ball Grid Array) structures or LGA (Land Grid Array) structures are known. Each of the semiconductor devices is made up of a structure in which a semiconductor element (semiconductor chip) is fixed on a wiring substrate, the electrodes of the semiconductor chip and the connecting pads that are formed by wiring of the wiring substrate are connected with conductive wires (connecting means), and the semiconductor chip, the wire and the like are covered with a sealing body made of an insulative resin. Further, in order to improve productivity, a manufacturing method using a so-called collective mold method is adopted. In this manufacturing method, a wiring mother board on which product forming parts for producing semiconductor devices are arranged longitudinally and laterally is prepared. Thereafter, a semiconductor chip is fixed to each of the product forming parts, connection of wires is performed, the entire wiring mother board is further covered with an insulative resin, the wiring mother board together with the resin is cut longitudinally and laterally to produce a plurality of semiconductor devices.
Meanwhile, as methods for achieving improvement of the degree of integration and reduction in size of a semiconductor device, a method for stacking semiconductor chips in which ICs and the like are formed, and a method for stacking packaged semiconductor devices and the like are adopted. Such methods are disclosed in Japanese Patent Laid-Open No. 2004-172157 and Japanese Patent Laid-Open No. 2004-273938.
As a semiconductor device which is publicly well known, a resin seal type semiconductor device is cited. The semiconductor device is made up of a structure in which a semiconductor chip is mounted on the top surface of a wiring substrate including external electrode terminals on the undersurface, the electrodes of the semiconductor chip are electrically connected to the wiring of the wiring substrate via connecting means, and the semiconductor chip and the connecting means are covered with a sealing body (package) made of an insulative resin. When such a semiconductor device is stacked, for example, a method for manufacturing the stacked type semiconductor device by projecting the outer peripheral portion of the wiring substrate on which a part of the wiring is exposed to the outer side of the sealing body, and for connecting the external electrode terminals (solder bumps) of the semiconductor device (the semiconductor device in the upper layer), which is to be stacked, to the exposed wiring portion is conceivable.
In such a structure, when semiconductor chips in two layers are disposed to be stacked in the package of the semiconductor device in the lower layer, the height of the package increases. Therefore, when the bump electrode is formed by one solder ball, the height becomes insufficient, and the upper and lower semiconductor devices sometimes cannot be electrically connected. In this case, a method is conceivable, in which a substrate for stacking is disposed in the middle layer, solder balls are attached to the top and bottom of the substrate, and the upper and lower semiconductor devices are electrically connected.
However, in the stacked type semiconductor device of such a structure, the height of the stacked type semiconductor device increases, and a reduction in thickness of the stacked type semiconductor device is difficult to achieve. Further, the wiring substrate portion for connecting the bump electrode is required at the outer side of the package, and reduction in size of the stacked type semiconductor device becomes difficult to achieve.
Further, Japanese Patent Application No. 2006-113529 discloses a package-on-package stacked type semiconductor device which was studied by the present inventors, though it was not known at the time of filing the present application. The outline of it will be described as follows. A lower semiconductor device is configured by a wiring substrate which includes wiring in a predetermined pattern, at least one semiconductor chip which is mounted on the wiring substrate with electrodes electrically connected to the wiring of the wiring substrate via connecting means, a sealing body made of an insulative resin, which is formed on the wiring substrate and which covers the semiconductor chip and the connecting means, a plurality of lands provided on a top surface of the sealing body, and connecting wires which extend from the wiring pattern of the wiring substrate to the side surface and the top surface of the sealing body, which are electrically connected to the land parts. The stacked type semiconductor device is configured by mounting the external terminals of the upper semiconductor device on a plurality of lands provided on the top surface of the sealing body of the lower semiconductor device.
In such a stacked type semiconductor device, the connecting wires provided at the sealing part are configured to be exposed, the connecting wires are touched when the semiconductor device is handled in the selecting step and the step of mounting to the mounting substrate, and the connecting wire may be damaged or broken. Further, when a foreign matter or the like is attached onto the connecting wire of the stacked type semiconductor device in the above described steps, the connecting wire may be short circuited. Further, even after the stacked type semiconductor device is mounted on the mounting substrate and incorporated into an electronic device, a short circuit may occur in the connecting wires because the connecting wires are exposed.
Further, in the stacked type semiconductor device, the connecting wires are formed to be exposed on the sealing part, and therefore, when the stacked type semiconductor device is mounted on compact mobile devices or the like such as a cellular phone, the lands and the connecting wires may come off the sealing part as a result of the impact of falling or the like, and the issue of connection strength may become a problem. Therefore, there is the possibility of being unable to secure sufficient reliability of the stacked type semiconductor device.